In the Official Gazette on Japanese Utility Model Publication No. 8264/1985, there is disclosed a water-pressure-operated gas valve of a faucet-controlled gas water heater in which primary and secondary valves are provided that open and close a gas passage of a main burner sequentially through the intermediary of a valve rod moving in accordance with the quantity of supplied water. The primary valve is devised so that conduit orifices on the top side of the secondary valve are opened and closed in a snapping manner by the movement of said valve rod through the intermediary of a disk-shaped leaf spring.
The secondary valve of the aforesaid water-pressure-operated gas valve, however, is an on-off valve which opens and closes in accordance with the water flow rate and thus it is not capable of adjusting the gas input, that is, the amount of combustion, in accordance with the water flow rate.
The present invention eliminates this disadvantage by constructing the secondary valve as a modulation valve whose opening is adjusted in accordance with the water flow rate; the correlative position of the secondary valve to an element operating in accordance with the quantity of supplied water is essential. When priority is given to this point in assembling, however, a number of components need to be interposed between said element and the secondary valve, and consequently an error tends to occur in the correlative position of the secondary valve to said element due to the integration error or assembly error of these components. When the aforesaid error is corrected, on the other hand, another error is caused in the positional relationships between the valve rod and a snap spring and between said snap spring and the primary valve.
In view of the existing state of the prior art, the present device is designed to attain a gas valve whose assembly is taken into consideration, and it is constructed in such a manner that the gas valve is reliably able to open and close the gas passage in accordance with the pressure of the supplied water. More particularly, a water-pressure-operated gas valve is provided with a primary valve and a secondary valve which open and close a gas passage of a main burner sequentially through the intermediary of a valve rod moving in accordance with the flow rate of supplied water. The primary valve is devised so that conduit orifices provided on the top side of the secondary valve, for conducting the minimum quantity of gas, are opened and closed in a snapping manner by the movement of a valve rod through the intermediary of a disk-shaped constant force spring. The secondary valve is constructed as a modulation valve whose opening is varied in accordance with the amount of movement of the valve rod, while a first adjusting screw is threaded in the top portion of the secondary valve so that it supports the constant force spring. The upper end of the valve rod, piercing through the secondary valve, is made to face the lower surface of the constant force spring, while a second adjusting screw threaded in the primary valve is provided so that the lower end thereof faces the constant force region of the constant force spring on the top surface thereof.